In the past century, wireless communication has evolved from an art form to science. In the early stages, people saw a cause-and-effect relationship between an electrostatic discharge and a received artifact (a smaller discharge on a disconnected device). This original understanding excited man's curiosity and experimentation. DeForest and Marconi, along with many others, translated that curiosity into a practical application of wireless communication. This technology has been evolving from the early rudimentary transmitters and receivers handling analogue voice to current digital systems handling voice and data in a seamless radio frequency network.
Traditionally, this technology has been referred to as Land Mobile Radio (LMR). In the United States, a single vendor dominates LMR technology. Characteristically, a single vendor dominated technology is slow to innovate and slow to adopt new technology. Project 25 is a set of standards produced by the joint effort of the Association of Public Safety Communications Officials (APCO), the National Telecommunications and Information Administration (NTIA) and the National Association for Telecommunications and Technology Professionals Serving State Government (NASTD) and standardized under the Telecommunications Industry Association (TIA) and represents a current LMR communication technology. Unfortunately, all current LMR communication technology, including Project 25, continues to suffer from lack of new applications.
LMR, in its current form, is a legacy technology in the mature stages of its life cycle. A basic tenet under the evolution of LMR technology was a predominant school of thought that wireless communications was best achieved over a specific frequency within the component of spectrum. This also lent itself nicely to federal management and regulation of the spectrum when demand was low.
Current systems do not provide the expanded, reliable communications communities (e.g., neighborhoods, boroughs, towns and cities) regard as necessary today, especially during disasters, natural or man-made. They do not support today's network voice, video and data requirements. They are also limited in terms of the number of simultaneous users they can accommodate. Today, interoperability, mobility, reliability, scalability and maintainability are major concerns to communities.
In recent years, the International Telecommunication Union (ITU) and the Federal Communication Commission (FCC) have begun to view radio frequency spectrum as more of a reusable resource. The results are additional frequency spectrum allocations supporting base band communication techniques allowing multiple users access to a single spectrum component (the concept of spectrum reuse). This new school of thought opens up possibilities for new digital networks to use frequency and bandwidth in ways previously inconceivable.
Unfortunately, this single concept is fundamentally incompatible with the traditional LMR systems. LMR systems use expensive repeater systems that, at best, allow two-way communications from one transmitter to many receivers with little or no concurrency.
Although LMR technology is basically the same as that used 50 years ago, it is still in use today because it meets a fundamental communication need: push-to-talk (PTT). However, it falls far short in two important areas. First, new technology now exists that may advantageously provide better interoperability. Second, LMR cannot be enhanced, adapted or evolved to meet the myriad of other communication needs of first responders, including broadband data and video.
First responders in communities would enjoy a distinct advantage by using the newer technology and retiring their LMR legacy systems. Economics and technology comparisons yield a compelling reason to make the change. Other technologies, such as cellular PTT and cellular digital packet data (CDPD) are not appropriate, because these are commercial technologies that proved a failure on Sep. 11, 2001, or will be phased out of service in 2004.
First responders have traditionally been dependent on what the major LMR vendor provided. In 1977, the LMR technology was upgraded from a simplex repeater system (developed during World War II) to a frequency hopping system (not to be confused with spread spectrum) that allowed multiple repeaters to coordinate the use of limited spectrum allocations. This new trunking system made more effective use of spectrum by time sharing across many talkgroups with intelligent radios that recognized subaudible and clear-to-send (CTS) tones that controlled the squelch and other aspects of the radio's operation.
Another major upgrade to these systems was introduced in 1987. This upgrade (called Trunking Systems II) expanded support for digital applications. The digital applications allow text messages to be transmitted and received by in-vehicle computers. These systems used existing licensed spectrum allocations and technology. The base-band technology frequency modulation (FM) is the carrier of voice and data in these systems. The drawback is that FM is not an efficient medium to transmit data.
Several years ago the ITU and the FCC allocated spectrum to unlicensed applications using spread spectrum technology in the ISM (Industrial Scientific and Medical) bands. Spread spectrum transmission and receiving technology had been developed during World War II. The technology has been slow to adopt because the coder/decoder (codec) is somewhat complex and the ITU and FCC concept of spectrum allocations date back to the Hoover administration and do not accommodate spread spectrum techniques. Originally, spread spectrum was developed to hide high-energy radar pulses in the background noise. For a number of years this was a classified application of the technology.
The technology drive for spread spectrum technology is primarily WiFi applications using the IEEE 802.11 standards. There are a number of standards in use and more to follow. These standards have been developed for non-mobile, short-range subscriber applications with relatively simple coder/decoder constructs. The evolution of these products has been the impetus driving the integrated circuit component requirements for more robust systems.
Because of the unique first responder communication requirements, the 802.11 standards are appropriate. IEEE did not design 802.11 to support the high speed mobile applications first responders require in a public safety communications infrastructure. Frequency spreading algorithms and coder/decoder components are much more complex for mobile applications.
Accordingly, what is needed in the art is a fundamentally new architecture for a public safety communications network that may serve one or more communities. What is needed in the art is a group of new devices and services that can be used alone or in combination to realize some or all of the advantages of the new architecture. More specifically, a better way to provide wireless access and routing is needed. A better way to ensure that devices are reliably powered is needed. A better wireless personal communication device is needed. A better way to manage a public safety network is needed. A better network management suite and device management services, network management strategy services and network management suite talkgroup services are also needed. Finally, a public safety communications infrastructure incorporating one or more of these aspects is needed.